Method for rapid pma alignment in 100gbase-kp4

ABSTRACT

Methods, apparatus and systems for implementing Physical Media Attachment (PMA) alignment and rapid transition from a link training mode to a data mode for next-generation high-speed Ethernet links including a 100 Gbps Ethernet link. Training frames are transmitted between first and second Ethernet interfaces on opposing ends of the link in a pair-wise manner, with a first training frame being sent from a first Ethernet interface and a second training frame being returned from the second Ethernet interface. The training frames have a length that is different that the length of Physical Media Attachment (PMA) frames, and the returned training frames include receiver readiness status indicia identifying a readiness status of a local receiver port, frame alignment offset data identifying a relative offset between a training frame and a predetermined location in a PMA frame, and countdown data. The readiness status indicia, frame alignment offset data and countdown data are employed to facilitate a rapid transition from the link training mode to the data mode.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of the filing date of U.S. Provisional Application No. 61/704,762, filed Sep. 24, 2012, entitled “PMA-SIZE TRAINING FRAME FOR 100 GBASE-KP4” under 35 U.S.C. §119(e). U.S. Provisional Application No. 61/704,762 is further incorporated herein in its entirety for all purposes.

FIELD OF THE INVENTION

The field of invention relates generally to Ethernet-based interconnects and, more specifically but not exclusively relates to techniques for implementing Physical Media Attachment (PMA) alignment and rapid transition from a link training mode to a data mode for high-speed Ethernet links

BACKGROUND INFORMATION

Ever since the introduction of the microprocessor, computer systems have been getting faster and faster. In approximate accordance with Moore's law (based on Intel® Corporation co-founder Gordon Moore's 1965 publication predicting the number of transistors on integrated circuits to double every two years), the speed increase has shot upward at a fairly even rate for nearly three decades. At the same time, the size of both memory and non-volatile storage has also steadily increased, such that many of today's personal computers are more powerful than supercomputers from just 10-15 years ago. In addition, the speed of network communications has likewise seen astronomical increases.

Increases in processor speeds, memory, storage, and network bandwidth technologies have resulted in the build-out and deployment of networks with ever substantial capacities. More recently, the introduction of cloud-based services, such as those provided by Amazon (e.g., Amazon Elastic Compute Cloud (EC2) and Simple Storage Service (S3)) and Microsoft (e.g., Azure and Office 365) has resulted in additional network build-out for public network infrastructure, in addition to the deployment of massive data centers to support these services which employ private network infrastructure.

A typical data center deployment includes a large number of server racks, each housing multiple rack-mounted servers or blade servers. Communications between the rack-mounted servers is typically facilitated using the Ethernet (IEEE 802.3) protocol over copper wire cables. In addition to the option of using wire cables, blade servers and network switches and routers may be configured to support communication between blades or cards in a rack over an electrical backplane or mid-plane interconnect.

In recent years, the speed of Ethernet connections over copper wiring has reached the 10 Gigabits per second (Gpbs) and 40 Gpbs level. Moreover, The IEEE (Institute of Electrical and Electronics Engineers) is currently developing a specification (IEEE 802.3bj) defining a new backplane PHY type called 100 GBASE-KP4 that is targeted for a bandwidth of 100 Gbps over electrical backplanes with a loss up to 33 dB at 7 GHz. A similar specification for a new 100 Gbps over a cable connection is also being defined by the IEEE. An important aspect for facilitating successful implementation of 100 Gbps links is link training, which includes PMA alignment and transition from a link training mode to a data mode.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing aspects and many of the attendant advantages of this invention will become more readily appreciated as the same becomes better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein like reference numerals refer to like parts throughout the various views unless otherwise specified:

FIG. 1 is a schematic diagram illustrating the structure of a 100 GBASE-KP4 link, according to one embodiment;

FIG. 2 is a diagram illustrating mapping for PAM4 encoding;

FIG. 3 is a training state diagram for a 10 GBASE-KR PHY;

FIG. 4 a is a block diagram showing the components of a training frame, according to one embodiment;

FIG. 4 b is a schematic diagram illustrating a training frame and exemplary signaling, according to one embodiment;

FIG. 5 a shows an exemplary structure for a Frame Marker and Coefficient Update portion of a training frame, according to one embodiment;

FIG. 5 b shows an exemplary structure for a Status Report portion of a training frame, according to one embodiment;

FIG. 6 is a diagram illustrating differential Manchester coding;

FIG. 7 is a table illustrating exemplary encodings for cells in Coefficient Update fields;

FIG. 8 is a table illustrating exemplary encodings for cells in Status Report fields;

FIG. 9 a is a schematic diagram illustrating the relationship between the Data Link and Physical layers of the OSI reference model and IEEE 802.3 LAN CSMA/CD LAN model layers corresponding to the current draft of 100 GBASE-KP4 defined in IEEE P802.3bj Draft 1.0;

FIG. 9 b is a schematic diagram illustrating further details of selected LAN CSMA/CD layers in FIG. 9 a;

FIG. 10 is a transmit adaption process diagram illustrating operations performed by the PMA sublayer during link up transmit operations.

FIG. 10 a is a transmit adaption process diagram illustrating operations performed by the PMA sublayer during transmission of the Frame Marker and Control Channel portions of a training frame; according to one embodiment;

FIG. 10 b is a transmit adaption process diagram illustrating operations performed by the PMA sublayer during transmission of the Training Pattern portion of a training frame; according to one embodiment;

FIG. 11 is a receive adaption process diagram illustrating operations performed by the PMA sub-layer during link up receive operations.

FIG. 11 a is a receive adaption process diagram illustrating operations performed by the PMA sublayer during receiving of the Frame Marker and Control Channel portions of a training frame; according to one embodiment;

FIG. 11 b is a receive adaption process diagram illustrating operations performed by the PMA sublayer during receiving of the Training Pattern portion of a training frame; according to one embodiment;

FIGS. 12 a and 12 b are data structure diagrams illustrating the Frame Marker and Coefficient Update portions of a Training Frame, and further illustrating respective parity schemes, according to one embodiment;

FIG. 13 is a diagram of a data structure illustrating a training frame, accordingly to one embodiment;

FIG. 14 is a graph illustrating signaling corresponding to a simulation of an exemplary training frame;

FIGS. 15 a and 15 b illustrate selection of four PRBS13 initiation states that are ¼ cycle apart;

FIG. 16 illustrates a plurality of training frames encapsulated in a PMA frames, along with a resulting advancement in the alignment offset between training frames and PMA frames of 16(mod 29);

FIG. 17 illustrates a training frame cycle employing 29 training frames per cycle and corresponding PMA alignment offset advancements between training frames of 16(mod 29);

FIG. 18 illustrates a message flow diagram depicting an exchange of training frames between components at opposing ends of a link, wherein training frame status report field data are illustrated that are employed for facilitating a rapid transition between a link training mode and a data mode;

FIG. 19 a is a frontal isometric view of an exemplary blade server chassis in which a plurality of server blades are installed;

FIG. 19 b is a rear isometric view of the blade server chassis of FIG. 16 a;

FIG. 19 c is an isometric frontal view of an exemplary blade server rack in which a plurality of rack-mounted blade server chassis corresponding to FIGS. 16 a and 16 b are installed; and

FIG. 20 shows details of the components of a typical server blade, according to one embodiment; and

FIG. 21 is a schematic diagram illustrating an architecture for a network node employing a network chip configured to perform link training and initialization operations in accordance with the embodiments disclosed herein.

DETAILED DESCRIPTION

Embodiments of methods, apparatus and systems for implementing PMA alignment and rapid transition from a link training mode to a data mode for a high-speed Ethernet link are described herein. In the following description, numerous specific details are set forth (such as implementation of a 100 Gbps Ethernet link) to provide a thorough understanding of embodiments of the invention. One skilled in the relevant art will recognize, however, that the invention can be practiced without one or more of the specific details, or with other methods, components, materials, etc. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of the invention.

Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, the appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

Embodiments for facilitating link training with rapid transition from link training mode to data mode for high-speed Ethernet links including the proposed 100 GBASE-KP4 PHY are disclosed herein. In order to preserve compatibility with existing training mechanisms, some aspects of link training for the 100 GBASE-KP4 PHY are common to similar aspects defined for the IEEE 10 GBASE-KR PHY, which is targeted at 10 Gbps links and is currently employed in various types of equipment such as switches and routers. Additionally, there are other common aspects that are defined in IEEE Std 802.3ap-2007. While these common aspects may be identified and briefly discussed herein, corresponding detailed discussions of how these aspects may operate or be implemented are generally not provided herein in order to not obscure inventive aspects of the embodiments. Other aspects of some embodiments are described in further detail in IEEE P802.3bj Draft 1.0 and IEEE P802.3bh Draft 3.1.

The Physical layer (also referred to a “PHY”) structure of one embodiment of a 100 GBASE-KP4 link is illustrated in FIG. 1. The PHY defines the physical structure of the interconnect and is responsible for dealing with details of operation of the signals on a particular link between two link partners, such as depicted by components A and B. This layer manages data transfer on the signal wires, including electrical levels, timing aspects, and logical issues involved in sending and receiving each bit of information across the parallel lanes. As shown in FIG. 1, the physical connectivity of each interconnect link is made up of four differential pairs of signals 100, comprising lanes 0-3 in each direction. Each port supports a link pair consisting of two uni-directional links to complete the connection between two components. This supports traffic in both directions simultaneously.

Components with 100 GBASE-KP4 ports communicate using a pair of uni-directional point-to-point links, defined as a link pair, as shown in FIG. 1. Each port comprises a Transmit (Tx) link interface and a Receive (Rx) link interface. For the illustrated example, Component A has a Tx port 102 that is connected to Component B Rx port 104. Meanwhile, Component B has a Tx port 104 that is connected to Component B Rx port 108. One uni-directional link transmits from Component A to Component B, and the other link transmits from Component B to Component A. The “transmit” link and “receive” link is defined relative to which component port is transmitting and which is receiving data. In the configuration illustrated in FIG. 1, the Component A transmit link transmits data from the Component A Tx port 102 to the Component B Rx port 104. This same Component A transmit link is the Port B receive link.

The 100 GBASE-KP4 PHY uses a 4-level pulse amplitude modulation (referred to as PAM4) signal to send and receive data across the channel. As shown in FIG. 2, PAM4 consists of four logical levels that are mapped as follows:

0 maps to −1 1 maps to −1/3 2 maps to +1/3 3 maps to +1 Logical levels 0 and 3 respectively correspond to low and high level signals having signal levels −1 and +1, while logical levels 1 and 2 correspond to intermediate level signals have signal levels −1/3 and +1/3.

The physical signaling for the 100 GBASE-KP4 PHY employs a Unit Interval (UI) of 1 bit having a time corresponding to 13.59375 Gbd symbols (˜73.6 psec). In one embodiment a Training Frame Word (TFW) of 46 UI is employed for link training. Each TFW corresponds to two full 46-bit terminated blocks (TB46).

In one embodiment, the format for the training sequence for the 100 GBASE-KP4 PHY is similar to that employed for the 10 GBASE-KR PHY defined in the IEEE Std. 802.3ap-2007 specification. The training state diagram for 10 GBASE-KR PHY is shown in FIG. 3. A significant difference between the 10 GBASE-KR PHY and the 100 GBASE-KP4 PHY is that the former defines a NRZ (Non-return to Zero) 2-level (PAM2) PHY rather than a 4-level PAM4 signal.

The 100 GBASE-KP4 link is established using the following sequence:

-   -   (1) Auto-negotiate capabilities to link partner     -   (2) Send out training sequence to tune PHY for the channel's         characteristics         -   Obtain Frame Lock         -   TX FFE handshake: Adapt Tx coefficients to channel             characteristics         -   DSP converged: Train Rx to channel         -   Status Exchange Ready or not?     -   (3) Countdown to data mode and Send out idle symbols

The training frame is a fixed length structure that is sent continuously during training As shown in FIG. 4 a, in one embodiment, a training frame 400 includes a Frame Marker 402 comprising 2 TB46 (1 TFW), a Control Channel including a Coefficient Update 404 comprising 8 TB46 (4 TFW) and a Status Report 406 comprising 10 TB46 (5 TFW), and a Training Pattern 408 comprising 364 TB46 (182 TFW) for a total of length of 384 TB46s or 192 TFWs. Further details of training frame 400 are shown in FIG. 4 b and discussed below.

In one embodiment, training Frames are delimited by the bit pattern, hexadecimal 3FFFFFF800000 (23 ones followed by 23 zeros in which the ones are +1 PAM4 symbols and the zeros are −1 PAM4 symbols), as expressed in 13.59375 Gbd symbols. This is illustrated by the Frame Markers shown in FIGS. 4 b, 5 a, 5 b, 12 a, 12 b, and 13 and 14.

The control channel is transmitted using differential Manchester encoding DME. An example of DME is shown in FIG. 6. The rules of differential Manchester encoding are as follows:

-   -   a) A data transition shall occur at each cell boundary.     -   b) A mid-cell data transition shall be used to signal a logical         one.     -   c) The absence of a mid-cell data transition shall be used to         signal a logical zero.         If a coding violation is detected within the bounds of the         control channel in a given training frame, the contents of the         control channel for that frame are ignored.

As shown in FIGS. 4 b, 5 a and 5 b, in one embodiment Coefficient Update 404 comprises a 16 data cell request, while Status Report 406 comprises a 20 data cell Status. The length for the cells in each of Coefficient Update 404 and Status Report 406 is 10 UI, and each of the 4 TFWs are configured as four cells followed by a 6 UI overhead field, resulting in a control channel length of 9×46=414 UI. In one embodiment at least a portion of the cells in Coefficient Update 404 are mapped to corresponding coefficient update fields defined for the 10 GBASE-KR PHY shown in FIG. 7, while at least a portion of the cells in Status Report 406 are mapped to corresponding status report fields in defined for the 10 GBASE-KR PHY shown in FIG. 8.

FIG. 9 a shows details of the relationship between the Data Link and Physical layers of the OSI reference model and IEEE 802.3 LAN CSMA/CD LAN model layers corresponding to the current draft of 100 GBASE-KP4 defined in IEEE P802.3bj Draft 1.2. FIG. 9 b shows further details of selected LAN CSMA/CD layers, including a MAC (Media Access Control) layer 900, a 100 GBASE-R Physical Coding Sublayer (PCS) sublayer 902, a Forward Error Correction (FEC) sublayer 904, a Physical Media Attachment (PMA) sublayer 906, a Physical Media Dependent (PMD) sublayer 908, and an Auto-Negotiation (AN) sublayer 910. Data is received in digital format as a binary bit stream by MAC layer 900, which processes and forwards the binary data to 100 GBASE-R PCS sublayer 902, which applies digital rules to the binary data to transform the data as described below. The transformed digital data are then passed to FEC sublayer 904, which performs Forward Error Correction. FEC uses the coding gain to increase the link budget and BER performance on a given channel. The link budget consists of the electrical parameters which define the connection between the transmit circuitry and the receive circuitry, such as insertion loss, return loss, pulse response, etc.

In the transmit direction, the role of PMA sublayer 906 is to adapt the signal output by FEC sublayer 904 to a PAM4 encoded signal to be passed to PMD sublayer 908 and AN sublayer 910 for transfer over the attached medium. One embodiment of the adaptation processes shown in FIG. 10 includes an insert overhead block 1002, an insert termination bits block 1004, a Gray coding block 1006, a [1/(1+D)mod 4] precoding block 1008, and a PAM4 encoding block 1010.

In further detail, incoming data 1000 in FIG. 10 is received by PMA sublayer 906 from FEC sublayer 904 comprising a PMA:IS_UNITDATA_i.request (where i=0 to 3) primitive used to define the transfer of four streams of a data from the PMA client to PMA. The data conveyed by PMA:IS_UNITDATA_(—)0.request to PMA:IS_UNITDATA_(—)3.request consists of four parallel streams of encoded bits, one stream for each of lanes 0-3. Each tx_bit parameter is either a ‘1’ or ‘0’. The start parameter is TRUE to indicate that the concurrent tx_bit is the first bit of the first, second, third, or fourth FEC symbol in the FEC codeword, or is otherwise FALSE. On each transaction, tx-bit is assigned F(i, m, n), where i is the lane number, m is an index indicating the FEC codeword number and increments at the start of each codeword, and n is an index indicating the bit number within the codeword.

Insert overhead block 1002 creates a sequence of overhead frames by inserting 40 overhead bits for every 31280 FEC bits. The FEC bits, F(i, m, n) are mapped into a continuous sequence of overhead frames. The overhead frame is 31320 bits in length. Each bit in the overhead frame is denoted V(i, p, q), where: i is the lane number; p is an index that indicates the frame number and increments at the start of each frame; and q is an index that indicates the bit number within a frame with a range 1 to 31320. The first 40 bits of the frame, V(i, p, 1) to V(i, p, 40) are the overhead bits. The next 31280 bits, V(i, p, 41) to Vi, p, 31320) are composed of the bits from 23 consecutive FEC codewords.

The overhead bits are inserted in the frame as follows:

-   -   V(i, p, 1)=H(i, p, 1)     -   V(i, p, 2)=H(i, p, 2)     -   V(i, p, . . . )=H(i, p, . . . )     -   V(i, p, 40)=H(i, p, 40)

The FEC codeword bits are aligned such that V(i, p, 41) is the first bit of a codeword, e.g., V(i, p, 41)=F(i, m, 1). The FEC bits are inserted into the frame in the order in which they were received from the FEC, e.g., V(i, p, 42)=F(i, m, 2), V(i, p, 43)=F(i, m, 3), and so on.

Insert termination bits block 1004 creates a sequence of termination blocks by inserting a two termination bits for every 90 overhead frame bits. The termination block is the 92 bits in length, the same as a TFW. Each bit in a termination block is denoted T(i, r, s), where: i is the lane number; r is an index indicating block number and increments at the start of each block; and s is an index indicating the bit number within a termination block with a range 1 to 92. The first two bits of each termination block, T(i, r, 1) and T(i, r, 2) are populated with the output of a PRBS13 Generator R(i, v), where T(i, r, 1)=R(i, v) and T(i, r, 2)=R(i, v+1). The remaining 90 bits of each termination block, T(i, r, 3) to T(i, r, 92), are overhead frame bits, as discussed above. The frame bits are aligned relative to the termination blocks such that the first bit of an overhead bit, V(i, p, 1), corresponds to the third bit of a termination block, T(i, r, 3). Overhead frame bits are mapped to the termination blocks in order of location within the overhead frame, e.g., T(i, r, 4)=V(i, p, 2), T(i, r, 5)=V(i, p, 3), and so on. The termination bit PRBS13 generator is initialized during the training process. When training is complete the state of the termination bit PRBS13 generator is retained and the resulting output is used for the termination bits in the PMA frame.

The PMA sublayer next maps consecutive pairs of bits to one of four Gray-coded via Gray coding block 1006. Each pair of bits, {A, B}, of each termination block are converted to a Gray-coded symbol with one of the four Gray-coded levels as follows:

-   -   {0, 0} maps to 0,     -   {0, 1} maps to 1,     -   {1, 1} maps to 2, and     -   {1, 0} maps to 3.

Gray-coded symbols corresponding to each termination block are denoted G(i, r, t), where: i is the lane number; r is an index indicating the termination block number; and t is an index indicating the symbol number within a termination block with a range 1 to 46. Pairing of bits is such that the first two bits of each termination block, T(i, r, 1) and T(i, r, 2), form a pair. Each bit pair {T(i, r, 2t−1), T(i, r, 2t)} maps to {A, B} and the Gray-coded result is assigned to G(i, r, t). The gray-coded symbol G(i, r, 1) is formed from the first two bits of a termination block, the termination bits, thus forming a termination symbol.

Precoding of the Gray-coded symbols is next performed by [1/(1+D)mod 4] precoding block 1008. The precoder output symbols are denoted, P(i, r, t), where: i is the lane number; r is an index indicating the termination block number; and t is an index indicating the symbol number within a termination block with a range 1 to 46. For each Gray-coded symbol G(i, r, t), a precoded symbol, P(i, r, t) is determined by the following algorithm:

If t = 1 then    P(i, r, t) = G(i, r, t) Else    P(i, r, ,t) = (G(i, r, t) − P(i, r, t−1)) mod 4 End If

The bits contributing to the Gray-coded termination symbol, G(i, r, 1), are the termination bits. The precoding algorithm applies this symbol directly to the output rather than combining it with the previous non-deterministic symbols and thus this termination symbol is always deterministic.

The last operation performed by PMA sublayer 906 is PAM4 encoding performed by PAM4 encoding block 1010. The PAM4 encoded symbols are denoted M(i, u), where i is the lane number and u is an index indicating the symbol number. Each consecutive precoder output symbol, P(i, r, t), is mapped to one of four PAM4 levels and assigned to the PAM4 encoder output M(i, u). Mapping from the precoder output symbol P(i, r, t) to a PAM4 encoded symbol M(i, u) is shown in FIG. 2 and discussed above.

In the received direction, the role of the 100 GBASE-KP4 PMA is to adapt the PAM4 encoded signal from the PMD to a FEC encoded signal to be passed to the FEC for further processing. One embodiment of the adaptation processes are shown in FIG. 11 and include a PAM4 decoding block 1100, a [(1+D)mod 4] coding block 1102, an inverse Gray coding block 1104, a remove termination bits block 1106, and a remove overhead block 1108. In general terms, each of these blocks performs an inverse operation to a corresponding block in FIG. 10 described above. Accordingly, further details are not provided herein.

To simplify the link establishment process discussed above when TRANSMIT(TRAINING) as shown in FIG. 3, the PAM4 multi-level signaling is not used for the Frame Marker, Coefficient Update, and Status Report data. During the transmission of Frame Marker 402, Coefficient Update 404, and Status Report 406, the PAM4 transmitter bypasses the overhead frame, termination block, gray coding, and 1/(1+D)mod 4 precoding stages of the PMA transmit and receive functional specifications. This is illustrated in FIG. 10 a, wherein data 1014 is redirected by a multiplexer (MUX) 1012 to PAM4 encoding block 1010, by passing each of insert overhead block 1002, insert termination bits block 1004, Gray coding block 1006, and [1/(1+D)mod 4] precoding block 1008. Therefore, the output levels are restricted to the −1 PAM4 symbol level for a logic 0 and the +1 PAM4 symbol level for a logic 1 to enable easy receiver lock to the training pattern over poor quality and non-equalized channels.

The corresponding receiver operations for processing received data during transmission of Frame Marker 402, Coefficient Update 404, and Status Report 406 are shown in FIG. 11 a. As illustrated, a MUX 1112 is configured to output data 1114 from PAM4 decoding block 1000, bypassing the operations of [(1+D)mod 4] coding block 1102, inverse Gray coding block 1104, remove termination bits block 1106, and remove overhead block 1108.

As discussed above, each TFW for the Coefficient Update 404 and Status Report 406 includes a 6 UI overhead field comprising 6 overhead bits. In one embodiment, the overhead bits are set to provide a DME logic value of ‘1’, e.g., coded as 000111 or 111000. This may be used to preserve DC balance for the TFW.

In one embodiment, a parity scheme is implemented through use of Coefficient Update and Status Report fields. Under one implementation, cell 6 of the coefficient update field table of FIG. 7 and cell 19 of the status report field table of FIG. 8 are used to transmit parity bits, as opposed to transmitting all 0's defined for this cell by the 10 GBASE-KR PHY specification. Two parity bits are calculated for each field (Coefficient Update and Status Report) separately, such that each field as a whole, including the parity bits, has even parity. The parity is the number of logical-one cells in the field, modulo 2 (not including the overhead bits). Under this parity scheme a parity check may be implemented to maintain DC balance of the control channel region and increase protection against false acceptance of sensitive messages, e.g., preset, init, and receiver ready. In one embodiment, if a parity violation is detected within the bounds of the respective field in a given training frame, the contents of that field within the control channel for that frame shall be ignored. For example, should only the parity of the coef update field be incorrect, then only the contents of the coef field will be ignored.

FIGS. 12 a and 12 b show respective examples of parity schemes, according to one embodiment. In FIG. 12 a, a bit pattern of 0000000000 is used for the parity bits in cell 6. In FIG. 12 b, a bit pattern of 1111100000 is used for the parity bits in cell 6.

In one embodiment, Training Pattern 408 uses the PMA transmit and receive functional specifications as currently defined in IEEE P802.3bj Draft 1.0 to enable the transmitter and receiver to exercise termination block, gray coding, and 1/(1+D)mod 4 precoding stages, while the overhead framer is bypassed. Corresponding block diagrams to facilitate the transmitter and receiver operations are shown in FIGS. 10 b and 11 b, respectively. Training Pattern 408 employs all four levels of PAM4 signaling to facilitate receiver calibration.

In one embodiment, input data 1016 to the termination block logic (i.e., insert termination bits block 1004 in FIG. 10 b) comprises a 13-bit Psuedo Random Bit Sequence known as PRBS13. PRBS13 is a 8191 bit sequence derived from the Fibonacci LFSR with polynomial function,

G(x)=1+x+x ² +x ¹¹ +x ¹³

In one embodiment, each TFW comprises 45 bits of PRBS13 data plus one termination bit. Two full sequences of PRBS13 data (8191 bits+182 termination bits for the first PRBS13, 8189 bits+182 termination bits for the second for a total of 16380 bits+364 termination bits) are transmitted during the 384 TB46 blocks corresponding to Training Pattern 408, as shown in FIGS. 4 b and 13. In one embodiment, the second PRBS13 sequence comprises a bit inversion of the first, minus the last two bits, as depicted by PRBS13a and PRBS13b in FIG. 4 b.

In addition to the example training pattern shown in FIG. 4 b, FIG. 14 shows an example training pattern generated during a simulated link training operation. Note the full swing signaling on the left portion of the diagram during the Frame Marker and control channel portion of the frame. Also note the 4-level signaling on right during the training pattern portion of the frame.

In one embodiment, the training pattern initial states for lanes 0-3 are derived in the following manner. Out of 8191 possible initial states in PRBS13, there are 34 for which the following process creates DC balanced results: Generate the full PRBS13 starting from the initial state, and then another full PRBS13 from the same state, inverted and apply most of the PMA data encoding (block termination, gray coding, 1/(1+D)mod 4 precoding and PAM4 mapping) to the data. From these 34 states, 22 have ‘0’ as a final precoder state, and four states are selected for which the output is DC balanced and final state of the precoder is ‘0’. In one embodiment, the initial four states are chosen such that the four resulting PAM4 sequences have low autocorrelation (except at offset 0) and low cross-correlation between each pair, as illustrated in FIG. 15 b. An exemplary set of initial states meeting the foregoing conditions include (initial bits sent on the data path, LSB first): S0=0x836F, S1=0x4007, S2=0xB947, S3=0xD3D4, as shown in FIG. 15 b. For each physical lane i=0.3, the training sequence shall start from state Si. This will also uniquely identify the lanes if they are swapped, and save lane order identification later on. For this choice of initial PRBS states, since the initial precoder state is 0, the final state is also 0. This has the benefit that the precoder state is known to be 0 upon switching to data mode (i.e., run-time link operation mode after link initialization). PRBS state and precoder state shall not advance during frame marker and control channel transmission.

Rapid Transition from Link Training Mode to Data Mode

During training mode, data is transmitted from a transmitter in a component at the first end of a link to a receiver in a component at the opposing (second) end of the link. Concurrently, data is transmitted from a transmitter in the component at the second end of the link to a receiver in the component at the first end of the link. This is schematically illustrated in FIG. 1, and discussed above. The objective of the training mode is to perform synchronization and tuning between the ports at each end of the link to enable accurate data transfer during data mode. During the training mode, sufficient synchronization and tuning will be obtained to enable transition to data mode, that is, the normal operational mode for the link during which data is transferred between the components at the opposing ends of the link.

Under one embodiment, a PMA frame having a length of 696 TB46 words is used for data modes. By contrast, the length of a training frame 400 is 384 TB46 words. In one embodiment, an alignment data variable called a pma_align_offset (PAO) marker is employed to indicate the relative location of the next training frame relative to the PMA frame as a 5-bit integer, wherein:

-   -   0: marker aligned with 40-bit overhead     -   1: marker is at offset of 24 words from 40-bit overhead     -   2 . . . 27     -   28: marker is at offset 28*24=672 words from 40-bit overhead     -   29 to 31: invalid, never transmitted, ignored on reception

During training mode and transition to data mode, training frames are transmitted sequentially, as shown in FIG. 16. While in link training mode, the training frames are not sent within PMA frames; however, the PMA framing logic and data paths are used to make the training frames.

In one embodiment, training frames are transmitted with an offset of 24*PAO, PAOε{0 . . . 28} TB46 blocks relative to the 40-bit overhead employed at the beginning of each PMA frame. This results in the offset being periodical with a cycle of 696/24=29 training frames. Under these parameters, the equation for PAO is,

PAO=mod(384*n,29)/24

wherein n is the training frame sequence number. This equation is derived from the generalized equation for k,

PAO=mod(l _(tf) *n,m)/(l _(pma) /m)

wherein l_(tf) is the length of the training frame, l_(pma) is the length of the PMA frame, m is the number of training frames in the offset cycle, and n is the training frame sequence number.

An example of one exemplary implementation following this scheme is shown in FIG. 16, wherein four training frames 400 a, 400 b, 400 c, and 400 d are transmitted back-to-back within 3 PMA frames 600 a, 600 b, and 600 c. In this example, the first training frame 400 a is transmitted so that it is aligned with the beginning of the first PMA frame 600 a, such that the offset between the beginning of the training frame and the beginning of the PMA frame is 0, and k=0. Under this initial condition (i.e., PAO=0), the next training frame will have an offset of 384 (PAO=16), following by 72 (PAO=3), 456 (PAO=19), and 144 (PAO=6), etc.

An illustration of a training frame cycle of 29 training frames along with corresponding PAO markers are shown in FIG. 17. In this example, training frame 1 (TF#1) includes a PAO value of 16, which is multiplied by 24 to indicate the relative location of the next training frame (TF#2) within the PMA frame. As illustrated, the next PAO value for TF#2 is 3, followed by 19, 6, 22, etc., with the PAO value advancing by 16 (mod 29) between training frames. The PAO values for the last two training frames in the cycle sequence are 13 and 0, which returns the cycle back to the starting alignment (which in this example indicates the beginning of the training frame is aligned with the 40-bit overhead of the PMA frame).

In one embodiment, PMA alignment offset data are used in combination with a countdown value to facilitate the transition from training mode to data mode. The use of the countdown value provides an indication to the receiving side that the transition will occur in j, j−1 . . . 1, 0 training frames, wherein a corresponding training_frame_countdown variable is employed to indicate the number of training frames remaining to be sent prior to data mode operation.

Returning to FIG. 8, the status field cells include three cells that are used for facilitating a rapid transition from training mode to data mode, which operate as follows. Upon detecting that sufficient synchronization and tuning has been establish on a link from a transmitter of a first component to a receiver of a second component, the transmitter of the second component returns a value of 1 in cell 6 of the status field to the receiver of the first component to indicate the local receiver has determined the training is complete and is prepared to receive data. A 5-bit pma_align_offset value is also returned in the status field via data in cells 11:7 (having a value of PAO=mod(384*n, 29)/24, as discussed above), along with a 2-bit training_frame_countdown value in cells 13:12, facilitating a countdown sequence of 2, 1, 0, as described below in further detail.

FIG. 18 shows an exchange of training frames and corresponding status field values employed to facilitate a transition from training mode to data mode for a link between components A and B employing PAO markers PAO and countdown values j. During training mode operation, component A transmits training frames 1800 from its transmitter (TX) port to component B, which receives the training frames at its receiver (RX) port. In response to each training frame 1800 that is received, component B transmits back a training frame 1802 including parameters in status cells corresponding to a Receiver Ready value, a POA marker, and a Countdown value. Prior to establishing sufficient synchronization and tuning, component B will return training frames having a Receiver Ready value of ‘0’, indicating that the local receiver (i.e., component B's RX port) is requesting training to continue. In one embodiment, training_frame_countdown value j is set to 3 when Receiver Ready is ‘0’. This is depicted by training frames 1800 a and 1802 a. During this timeframe prior to the local receiver indicating it is ready to transition to data mode, the POA marker PAO value and countdown j value may be ignored; in various embodiments the POA marker PAO may be calculated in the normal manner for each frame and included in the Status Report field data or simply set at a predetermined value, while the countdown j value may likewise be set at a predetermined value. Whether or not the POA marker PAO is included during this timeframe, the local receive will continue to update its PAO marker PAO value.

In response to receiving a training frame 1800 b, component B's local receiver indicates training is complete and it is ready to receive data, i.e., transition to data mode, by returning a training frame 1802 b with a Receiver Ready value of ‘1’. Also returned in training frame 1082 b is a POA marker value PAO corresponding to an advancement of 16(mod 29) between training frames 1802 a and 1802 b, as depicted by POA_(n+1), along with a countdown value set to j, the initial countdown value. In one embodiment the value of j is set to ‘3’. Under this nomenclature, n+1 means the next value for n, i.e., an advancement of PAO by 16(mod 29).

In one embodiment, in order to transition to data mode components at both ends of the link must be asserting Receiver Ready=1 (asserting Receiver_Ready). Once Receiver_Ready is asserted by both components, a Wait_Timer period is initiated during which approximately 100-300 training frames will be sent before transitioning to data mode. Toward the end of the Wait_Timer period, the countdown sequence will begin, thus identifying exactly when the transition to data mode will occur. Once the training_frame_countdown value reaches 0, the next portion of data that is received (following the current training frame) will comprise data mode data, beginning at an offset from the start of the PMA frame indicated by the pma_align_offset value (multiplied by 24).

Continuing at training frames 1800 c and 1802 c, the returned status field values include Receiver Ready=1, a POA marker value of POA_(n+2) indicating another advancement of 16(mod 29), along with a countdown value j−1, indicating the countdown value has been decremented by one. The countdown sequence continues until the countdown value=0, as depicted by training frames 1800 d and 1802 d. At this point, the local transmitter (Component A's TX port) has been informed that the other component's receiver is configured to transition to data mode.

Continuing on at the lower portion of FIG. 18, once transition to data mode is completed, the next frame to be transmitted is a data frame that begins relative to a PMA frame 600-1 at an alignment offset defined by the value POA_(n+j+1). The PAM frames transmitted from component A's TX port going forward (depicted by PMA frames 600-2 and 600-3) will comprise data frames having a format in accordance with the applicable format used for transferring data during data mode operations.

Exemplary Implementation Environment and Blade Server architecture

It is envisioned that aspects of the embodiments herein may be implemented in various types of computing and networking equipment, such as switches, routers and blade servers such as those employed in a data center and/or server farm environment. Typically, the servers used in data centers and server farms comprise arrayed server configurations such as rack-based servers or blade servers. These servers are interconnected in communication via various network provisions, such as partitioning sets of servers into LANs with appropriate switching and routing facilities between the LANs to form a private Intranet. For example, cloud hosting facilities may typically employ large data centers with a multitude of servers.

As an overview, typical blade server components and systems are shown in FIGS. 16 a-c, and 17. Under a typical configuration, a rack-mounted chassis 1600 is employed to provide power and communication functions for a plurality of server blades (i.e., blades) 1602, each of which occupies a corresponding slot. (It is noted that all slots in a chassis do not need to be occupied.) In turn, one or more chassis 1600 may be installed in a blade server rack 1603 shown in FIG. 16 c. Each blade is coupled to an interface plane 1604 (i.e., a backplane or mid-plane) upon installation via one or more mating connectors. Typically, the interface plane will include a plurality of respective mating connectors that provide power and communication signals to the blades. Under current practices, many interface planes provide “hot-swapping” functionality—that is, blades can be added or removed (“hot-swapped”) on the fly, without taking the entire chassis down through appropriate power and data signal buffering.

A typical mid-plane interface plane configuration is shown in FIGS. 16 a and 16 b. The backside of interface plane 1604 is coupled to one or more power supplies 1606. Oftentimes, the power supplies are redundant and hot-swappable, being coupled to appropriate power planes and conditioning circuitry to enable continued operation in the event of a power supply failure. In an optional configuration, an array of power supplies may be used to supply power to an entire rack of blades, wherein there is not a one-to-one power supply-to-chassis correspondence. A plurality of cooling fans 1608 are employed to draw air through the chassis to cool the server blades.

An important feature required of all blade servers is the ability to communicate externally with other IT infrastructure. This is typically facilitated via one or more network connect cards 1610, each of which is coupled to interface plane 1604. Generally, a network connect card may include a physical interface comprising a plurality of network port connections (e.g., RJ-45 ports), or may comprise a high-density connector designed to directly connect to a network device, such as a network switch, hub, or router.

Blade servers usually provide some type of management interface for managing operations of the individual blades. This may generally be facilitated by a built-in network or communication channel or channels. For example, one or more buses for facilitating a “private” or “management” network and appropriate switching may be built into the interface plane, or a private network may be implemented through closely-coupled network cabling and a network. Optionally, the switching and other management functionality may be provided by a management switch card 1612 that is coupled to the backside or frontside of the interface plane. As yet another option, a management or configuration server may be employed to manage blade activities, wherein communications are handled via standard computer networking infrastructure, for example, Ethernet.

With reference to FIG. 17, further details of an exemplary blade 1700 are shown. As discussed above, each blade comprises a separate computing platform that is configured to perform server-type functions, i.e., is a “server on a card.” Accordingly, each blade includes components common to conventional servers, including a main printed circuit board (main board) 1701 providing internal wiring (i.e., buses) for coupling appropriate integrated circuits (ICs) and other components mounted to the board. These components include one or more processors 1702 coupled to system memory 1704 (e.g., some form of Random Access Memory (RAM)), cache memory 1706 (e.g., SDRAM), and a firmware storage device 1708 (e.g., flash memory). A NIC (network interface controller) chip 1710 is provided for supporting conventional network communication functions, such as to support communication between a blade and external network infrastructure. Other illustrated components include status LED (light-emitting diodes) 1712, a set of RJ-45 console ports 1714 (only one of which is shown for simplicity), and a NIC 1715 coupled to an interface plane connector 1716. Additional components include various passive components (i.e., resistors, capacitors), power conditioning components, and peripheral device connectors.

Generally, each blade 1700 may also provide on-board storage. This is typically facilitated via one or more built-in disk controllers and corresponding connectors to which one or more disk drives 1718 are coupled. For example, typical disk controllers include SATA controllers, SCSI controllers, and the like. As an option, the disk drives may be housed separate from the blades in the same or a separate rack, such as might be the case when a network-attached storage (NAS) appliance or backend storage sub-system that is employed for storing large volumes of data.

NIC 1710 comprises circuitry and logic for facilitating corresponding networking operations, such as support for physical layer (L1) and data link layer operations (L2). Typically, upper layer operations are facilitated by an operating system network stack that would be hosted by an operating system running on processor 1702. However, in some embodiments, a NIC may employ its own network stack via embedded logic or the like.

In a typical data center deployment, network switching elements comprise rack-mounted equipment, such as would occupy a 1U, 2U, or 4U slot, or may be implemented via one or more server blades. Optionally, a network switching element may be implemented use one or more server blades.

NIC 1715 comprises circuitry and logic for implementing high-speed communication between multiple blades 1700 via interface plane 1604. In one embodiment, NIC 1715 is configured to implement signaling and logic corresponding to the 100 Gbps embodiments disclosed herein, including circuitry and logic for implementing a 100 GBASE-KP4 port and associated link training operations. To further facilitate inter-blade communication over the 100 GBASE-KP4 PHY, interface plane 1604 includes appropriate connectors, circuitry and wiring for facilitating the physical media aspect of the PHY (wiring not shown). For example, the circuitry may comprise connectors and wiring for facilitating signaling over 8 differential pairs in accordance with the configuration shown in FIG. 1.

In general, aspects of the link training embodiments disclosed herein may be implemented hardware (via, e.g., embedded logic), or via a combination of hardware and software. For example, a network element may include a processor running a software-based network stack and associated logic implemented via software for performing aspects of the operations described herein. Optionally, similar logic could be implemented via embedded logic in a NIC, large-scale network interface, or the like.

In addition to implementation in a blade server, the principles and teachings herein may be implemented via other types of equipment, such as telecommunications routers and switches. For example, a typical telecom switch comprises a rack with multiple cards coupled to a backplane, wherein the cards are generally analogous to the blades and the backplane is analogous to the interface plane in a blade server. Accordingly, the cards would be configured with circuitry and logic for implemented 100 GBASE-KP4 ports, and the backplane would include connectors, circuitry, and wiring for facilitating the physical media aspect of the 100 GBASE-KP4 PHY.

FIG. 21 shows an architecture 2100 for a network node employing a network chip 2102 configured to perform link training and initialization operations in accordance with aspects of the embodiments disclosed herein. Network chip 2102 comprises PHY circuitry 2104 including a PCS module 2106, an auto-negotiation module 2108, a link training module 2110, a transmitter port 2112 including transmitter circuitry 2113 and a receiver port 2114 including receiver circuitry 2115. Network chip 2102 further includes a DMA (Direct Memory Access) interface 2116, a Peripheral Component Interconnect Express (PCIe) interface 2118, a MAC module 2120 and a Reconciliation Sublayer (RS) module 2122. Network node 2100 also comprises a System on a Chip (SoC) 2124 including a Central Processing Unit (CPU) 2126 having one or more processor cores, coupled to a memory interface 2128 and a PCIe interface 2130 via an interconnect 2132. Memory interface 2128 is further depicted as being coupled to memory 2134. Under a typical configuration, network chip 2102, SoC 2124 and memory 2134 will be mounted on or otherwise operatively coupled to a circuit board 2136 that includes wiring traces for coupling these components in communication, as depicted by single lines connecting DMA 2116 to memory 2134 and PCIe interface 2118 to PCIe interface 2130 at a PCIe port 2138.

In one embodiment, MAC module 2120 is configured to implement aspects of the MAC layer operations performed by embodiments described herein. Similar, RS module 2122 is configured to implement reconciliation sub-layer operations performed by embodiments described herein, such as illustrated in FIG. 9 a.

Link training module 2110 is further depicted as including training frames 2140, which are configured in accordance with the training frame embodiments disclosed herein. Auto-negotiation module 2108 is further depicted as including a base page 2142. During link initialization, auto-negotiation module 2108 is implemented for auto-negotiation of link speed and capabilities. The auto-negotiation format consists of a base-page (e.g., base page 2142), which is the first set of formatted information exchanged with the link partner, as depicted by a link partner 2144 including a receiver port 2146 and a transmitter port 2148. In one embodiment the configuration of node 2100 and link partner 2144 are similar. In one embodiment, the format of base page 2142 is in accordance with the base page format defined in IEEE 802.3ap, the 10 GBASE-KR specification. Link training module 2110 is further configured to perform link training operations relating to initialization for a link 2150 communicatively coupled between network chip 2102 and link partner 2144 in accordance with aspects of the embodiments disclosed herein.

In one embodiment, network chip 2102 comprises a 100 Gbps Ethernet Network Interface Controller (NIC) chip. However, the circuitry and components of network chip 2102 may also be implemented in other types of chips and components, including SoCs, multi-chip modules, and NIC chips including support for multiple network interfaces (e.g., wired and wireless).

Although some embodiments have been described in reference to particular implementations, other implementations are possible according to some embodiments. Additionally, the arrangement and/or order of elements or other features illustrated in the drawings and/or described herein need not be arranged in the particular way illustrated and described. Many other arrangements are possible according to some embodiments.

In each system shown in a figure, the elements in some cases may each have a same reference number or a different reference number to suggest that the elements represented could be different and/or similar. However, an element may be flexible enough to have different implementations and work with some or all of the systems shown or described herein. The various elements shown in the figures may be the same or different. Which one is referred to as a first element and which is called a second element is arbitrary.

In the description and claims, the terms “coupled” and “connected,” along with their derivatives, may be used. It should be understood that these terms are not intended as synonyms for each other. Rather, in particular embodiments, “connected” may be used to indicate that two or more elements are in direct physical or electrical contact with each other. “Coupled” may mean that two or more elements are in direct physical or electrical contact. However, “coupled” may also mean that two or more elements are not in direct contact with each other, but yet still co-operate or interact with each other.

An embodiment is an implementation or example of the inventions. Reference in the specification to “an embodiment,” “one embodiment,” “some embodiments,” or “other embodiments” means that a particular feature, structure, or characteristic described in connection with the embodiments is included in at least some embodiments, but not necessarily all embodiments, of the inventions. The various appearances “an embodiment,” “one embodiment,” or “some embodiments” are not necessarily all referring to the same embodiments.

Not all components, features, structures, characteristics, etc. described and illustrated herein need be included in a particular embodiment or embodiments. If the specification states a component, feature, structure, or characteristic “may”, “might”, “can” or “could” be included, for example, that particular component, feature, structure, or characteristic is not required to be included. If the specification or claim refers to “a” or “an” element, that does not mean there is only one of the element. If the specification or claims refer to “an additional” element, that does not preclude there being more than one of the additional element.

The above description of illustrated embodiments of the invention, including what is described in the Abstract, is not intended to be exhaustive or to limit the invention to the precise forms disclosed. While specific embodiments of, and examples for, the invention are described herein for illustrative purposes, various equivalent modifications are possible within the scope of the invention, as those skilled in the relevant art will recognize.

These modifications can be made to the invention in light of the above detailed description. The terms used in the following claims should not be construed to limit the invention to the specific embodiments disclosed in the specification and the drawings. Rather, the scope of the invention is to be determined entirely by the following claims, which are to be construed in accordance with established doctrines of claim interpretation. 

What is claimed is:
 1. A method for facilitating a transition between a link training mode and a data mode for a high-speed Ethernet link, comprising: transmitting training frames from a transmitter port of a first component to be received at a receiver port of a second component, the training frames having a first length and being transmitted using Physical Media Attachment (PMA) framing logic employing frames having a second length different than the first length; receiving training frames transmitted from a transmitter port of the second component at a receiving port of the first component, the training frames that are received including receiver readiness status indicia identifying a readiness status of the receiver port of the second component to receive data, frame alignment offset data identifying a relative offset between a start of a training frame and a predetermined location in a PMA frame, and countdown data; and employing the receiver readiness status indicia, the frame alignment offset data and the countdown data to facilitate the transition between the link training mode and the data mode.
 2. The method of claim 1, wherein a current training frame that is received includes data identifying a relative offset between the start of a following training frame and the predetermined location in the PMA frame.
 3. The method of claim 2, wherein the predetermined location in the PMA frame is a 40-bit overhead for the PMA frame.
 4. The method of claim 1, wherein a training frame comprises a frame marker portion, a control channel portion, and a training pattern portion, and wherein the receiver readiness status indicia, the frame alignment offset data, and the countdown data are included in the control channel portion of the training frame.
 5. The method of claim 4, wherein the control channel portion of the training frame includes a coefficient update portion and a status report portion including cells in which the receiver readiness status indicia, the frame alignment offset data, and the countdown data are stored.
 6. The method of claim 5, wherein each of the coefficient update portion and status report portion include data that is encoded using differential Manchester encoding (DME), and further wherein each of the control channel portion and status report portion include overhead bits that are selected to effect DC balance.
 7. The method of claim 4, wherein the control channel portion of the training frame includes a coefficient update portion and a status report portion, and wherein separate parity bits are employed for each of the coefficient update portion and the status report portion.
 8. The method of claim 1, wherein a training frame has a first length and a PMA frame has a second length longer than the first length, and the frame alignment offset data is encoded as a integer derived as a function of the first and second lengths and a number of training frames in an alignment cycle between the training frames and the PMA frames.
 9. The method of claim 8, wherein the function is defined by the equation: PAO=mod(l _(tf) *n,m)/(l _(pma) /m) wherein l_(tf) is the length of the training frame, l_(pma) is the length of the PMA frame, m is the number of training frames in the offset cycle, and n is the training frame sequence number.
 10. The method of claim 8, wherein the function is defined by the equation: PAO=mod(384*n,29)/24 wherein n is the training frame sequence number.
 11. The method of claim 1, wherein the training frame comprises a plurality of 46-bit terminated blocks (TB46), and the training frame has a length of 384 TB46.
 12. The method of claim 1, wherein the training frame includes a training pattern, the method further comprising employing a 13-bit Pseudo-Random Bit Sequence (PRBS13) bit pattern for at least a portion of the training pattern.
 13. The method of claim 12, wherein a PRBS13 initial state is selected from among PRBS13 initial states that are DC balanced when used with a termination process, a Gray coding process, a precoding process and a PAM4 encoding process and for which the final state of a precoder operation is ‘0’.
 14. The method of claim 13, wherein the Ethernet link comprises a multi-lane link employing four lanes, and PRBS13 initial states are selected for respective lanes such the resulting PAM4 sequences have low cross-correlation relative to each other.
 15. The method of claim 1, wherein the Ethernet link comprises a multi-lane link including multiple lanes, further comprising transmitting training frames over each of multiple lanes.
 16. The method of claim 1, wherein the Ethernet link comprises a physical media implemented via wiring in one of a mid-plane or back-plane.
 17. The method of claim 1, wherein the high-speed Ethernet link supports a bandwidth of 100 Gigabits per second.
 18. An apparatus including a high-speed Ethernet interface having a transmitter port and a receiver port, the apparatus configured to perform operations when the apparatus is operating comprising: transmitting, during a link training mode, training frames from the transmitter port of the high-speed Ethernet interface to be received at a receiver port of a second apparatus, the training frames having a first length and being transmitted using Physical Media Attachment (PMA) framing logic employing frames having a second length different than the first length; receiving training frames transmitted from a transmitter port of the second apparatus at the receiving port of the high-speed Ethernet interface, the training frames that are received including receiver readiness status indicia identifying a readiness status of the receiver port of the second component to receive data, frame alignment offset data identifying a relative offset between a start of a training frame and a predetermined location in a PMA frame, and countdown data; and employing the receiver readiness status indicia, the frame alignment offset data and the countdown data to facilitate a transition between the link training mode and a data mode.
 19. The apparatus of claim 18, wherein a training frame has a first length and a PMA frame has a second length longer than the first length, and the frame alignment offset data is encoded as a integer derived as a function of the first and second lengths and a number of training frames in an alignment cycle between the training frames and the PMA frames.
 20. The apparatus of claim 19, wherein the function is defined by the equation: PAO=mod(l _(tf) *n,m)/(l _(pma) /m) wherein l_(tf) is the length of the training frame, l_(pma) is the length of the PMA frame, m is the number of training frames in the offset cycle, and n is the training frame sequence number.
 21. The apparatus of claim 19, wherein the function is defined by the equation: PAO=mod(384*n,29)/24 wherein n is the training frame sequence number.
 22. The apparatus of claim 18, wherein the training frame comprises a plurality of 46-bit terminated blocks (TB46), and the training frame has a length of 384 TB46 and the PMA frame has a length of 696 bits.
 23. The apparatus of claim 18, wherein the high-speed Ethernet transmitter port is configured to implement a multi-lane link including multiple lanes, and the Ethernet transmitter port is further configured to transmit training frames over each of multiple lanes.
 24. The apparatus of claim 18, wherein the high-speed Ethernet transmitter port supports a bandwidth of 100 Gigabits per second.
 25. The apparatus of claim 18, further comprising a high-speed Ethernet receive port configured to receive training frames from the second apparatus.
 26. A system comprising: a chassis; an inter-plane, mounted within the chassis, having first and second inter-plane connectors and wiring coupled therebetween configured to facilitate a 100 Gigabits per second (Gbps) Ethernet link; a first board having a first network interface controller (NIC) including 100 Gbps Ethernet transmitter and receiver ports operatively coupled to a first board connector that is coupled to the first inter-plane connector; a second board having a second NIC including 100 Gbps Ethernet transmitter and receiver ports operatively coupled to a second board connector that is coupled to the second inter-plane connector, wherein the first NIC is configured to perform operations when the system is operating including, transmitting, during a link training mode, training frames from the transmitter port of the first NIC to the receiver port of the second NIC, the training frames having a first length and being transmitted using Physical Media Attachment (PMA) framing logic employing frames having a second length different than the first length; receiving training frames transmitted from the transmitter port of the second NIC at the receiving port of the first NIC, the training frames that are received including receiver readiness status indicia identifying a readiness status of the receiver port of the second component to receive data, frame alignment offset data identifying a relative offset between a start of a training frame and a predetermined location in a PMA frame, and a countdown data value; and employing the receiver readiness status indicia, the frame alignment offset data and the countdown data to facilitate a transition between the link training mode and a data mode.
 27. The system of claim 26, wherein a training frame has a first length and a PMA frame has a second length longer than the first length, and the frame alignment offset data is encoded as a integer derived as a function of the first and second lengths and a number of training frames in an alignment cycle between the training frames and the PMA frames.
 28. The system of claim 27, wherein the function is defined by the equation: PAO=mod(l _(tf) *n,m)/(l _(pma) /m) wherein l_(tf) is the length of the training frame, l_(pma) is the length of the PMA frame, m is the number of training frames in the offset cycle, and n is the training frame sequence number.
 29. The system of claim 27, wherein the function is defined by the equation: PAO=mod(384*n,29)/24 wherein n is the training frame sequence number.
 30. The system of claim 26, wherein the training frame comprises a plurality of 46-bit terminated blocks (TB46), and the training frame has a length of 384 TB46 and the PMA frame has a length of 696 bits.
 31. An apparatus, comprising: Physical Layer (PHY) circuitry, including, a Physical Coding Sublayer (PCS) module; an auto-negotiation module; a link training module; a transmitter port including transmitter circuitry; and a receiver port including receiver circuitry; a Media Access Control (MAC) module; a Reconciliation Sublayer (RS) module; and a Peripheral Component Interconnect Express (PCIe) interface; wherein the apparatus is configured to perform operations when operating including, transmitting, during a link training mode, training frames via the transmitter port to a receiver port of a link partner, the training frames having a first length and being transmitted using Physical Media Attachment (PMA) framing logic employing frames having a second length different than the first length; receiving training frames transmitted from a transmitter port of the link partner at the receiver port of the apparatus, the training frames that are received including receiver readiness status indicia identifying a readiness status of the receiver port of the link partner to receive data, frame alignment offset data identifying a relative offset between a start of a training frame and a predetermined location in a PMA frame, and a countdown data value; and employing the receiver readiness status indicia, the frame alignment offset data and the countdown data to facilitate a transition between the link training mode and a data mode.
 32. The apparatus of claim 31, wherein a training frame has a first length and a PMA frame has a second length longer than the first length, and the frame alignment offset data is encoded as a integer derived as a function of the first and second lengths and a number of training frames in an alignment cycle between the training frames and the PMA frames.
 33. The apparatus of claim 32, wherein the function is defined by the equation: PAO=mod(l _(tf) *n,m)/(l _(pma) /m) wherein l_(tf) is the length of the training frame, l_(pma) is the length of the PMA frame, m is the number of training frames in the offset cycle, and n is the training frame sequence number.
 34. The apparatus of claim 32, wherein the function is defined by the equation: PAO=mod(384*n,29)/24 wherein n is the training frame sequence number.
 35. The apparatus of claim 31, wherein the apparatus comprises a 100 Gigabits per second Ethernet Network Interface Controller. 